The "dudud dudud dudududu" sound in the meme is completely different to the dial-up modem handshake sound "skreeee-chirrup-buzzzzwheee-krkkrkkrk-shhhhh".

The "dudud dudud dudududu" sound happens BEFORE an incoming mobile phone call. The "skreeee-chirrup-buzzzzwheee-krkkrkkrk-shhhhh" sound happens after an incoming land-line call is picked up.

Source: I used to host a BBS with a Hayes 2400 bps modem.